1. Field of the Invention
The present invention relates to a heat analysis apparatus for measuring the variation of the property of a sample according to the temperature variation. In Particular, the invention relates to a differential scanning calorimeter for measuring the amount of heat that a sample emits or absorbs in spare, compared with that of the reference sample on the basis of the temperature difference (differential heat) between the sample and a reference sample when the temperature of both of the samples varies.
2. Description of the Related Art
A differential scanning calorimeter is an apparatus for detecting differentially the amount of heat that a sample emits or absorbs in spare compared with a reference sample on condition that the measured sample and the reference sample to be stable thermally such as aluminum are arranged side by side when the temperature of both of the samples varies at constant rate. More specifically, the differential scanning calorimeter may include a cylinder-shaped heating furnace with a bottom plate, a heater for heating the heating furnace from the outer circumference, a heat buffer plate secured on the bottom plate of the heating furnace, a ring-shaper upper support plate and a lower support plate disposed on the heat buffer plate, a plate-shaped transmitting plate inserted between the upper support plate and the lower support plate to be secured by brazing and a sample container and a reference container placed on the heat transmitting plate (referring to JP-A-2000-28559). According to the above known apparatus, material with high heat conductivity such as silver is selected for the material of the heating furnace. In the meanwhile, in order to make the heat buffer plate and the heat transmitting plate, material with heat conductivity lower than that of the material for the heating furnace such as constantan is selected. According to the differential scanning calorimeter, heat of the heater is transmitted to the sample container and the reference container through the heat transmitting plate and the heat amount of the measured sample contained in the sample container can be detected differentially by measuring the temperature difference between both of the sample and reference containers. In particular, referring to JP-A-2000-28559, the heat of the heater can be transmitted to the heat transmitting plate via the heat buffer plate and the lower support plate from the heating furnace. Hence the temperature difference between the sample container and reference container can be avoided due to the occurrence of the temperature distribution over the heating furnace along the direction where the sample container and the reference container are arranged.
However, if the contact condition between the transmitting plates to install the sample container and the reference container and the ring-shaped lower support plate to transmit heat to the heat transmitting plate is not uniform in the known differential scanning calorimeter, as disclosed in JP-A-2000-28559, the heat amount of the sample container coming from the heat transmitting plate is not the same as that of the reference container. For example, if pores are formed in a potion of the blazing for securing the heat transmitting plate to the lower support plate, the heat conductivity of a portion with the pores may differ from that of a portion without pores.
That is, the amount of heat incoming from the sample container may differ from that incoming from the reference container due to the relationship of locations among the sample container, the reference container and the range of portion with pores. Therefore, the known apparatus has disadvantage that the amount of heat which the sample emits or absorbs in spare compared with that of the reference sample on the basis of the difference of both temperatures can not be detected exactly.
The heat emitted from the heater may contain noise components that perhaps differ place to place along the circumference of the heating furnace such as the fluctuation temperature. If the noise components are transmitted to the sample container and the reference container via the heating furnace, the heat buffer plate, the lower support plate and the heat transmitting plate from the heater, then the detected temperature difference may contain noise components due to the noise components of the incoming heat. Hence, the known apparatus has a problem that the amount of heat that the sample emits or absorbs in spare compared with that of the reference sample cannot be detected exactly.